Does Ontario's Code say what backfill can touch a waterproofed wall?

Ontario's Building Code does address this. Clause 9.12.3 sets out what backfill placed against a foundation wall must meet.

The requirements cover three things. The backfill must be placed so it does not damage the wall, the drain tile, any insulation, or the waterproofing or dampproofing membrane. Within 600 mm of the foundation, it must be free of debris and boulders larger than 250 mm. And it must be graded to prevent drainage toward the foundation after settling.

Those rules apply regardless of whether the wall is dampproofed or waterproofed. The Code does not name a specific fill material or gradation for the zone against a waterproofed wall beyond those three conditions, so the contractor's method for protecting the membrane during backfilling matters. Clause 9.13.3.4 adds that a waterproofed surface must be protected from damage during backfilling; the Code does not name the protection material.

A fair quote for exterior waterproofing should spell out how the membrane will be protected before the trench is filled: what material goes against the membrane, how the backfill is placed and compacted, and how the finished grade will slope away from the wall. Ask the contractor to describe this in writing.

Ask for the written scope to show exactly what goes between the membrane and the backfill, and what happens if the membrane is found to be damaged when the trench is open.